Substrate holder, plating apparatus, and plating method

ABSTRACT

A substrate holder holds a substrate while hermetically sealing an outer circumferential edge and a reverse side of the substrate and exposing a surface of the substrate. The substrate holder has a base and a cover having an opening defined therein and positioned to place the substrate between the base and the cover. An attracting mechanism couples the base and the cover to each other to hold the substrate between the base and the cover, with the surface of the substrate being exposed through the opening.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate holder for use in a platingapparatus for plating a to-be-plated surface of a substrate, especiallyto form a plated film in fine trenches for interconnection, holes, andresist openings in the surface of a semiconductor wafer, or to producebumps (protrusive electrodes) on the surface of a semiconductor waferfor electric connection to package electrodes or the like, a platingapparatus having such a substrate holder, and a plating method usingsuch a substrate holder.

2. Description of the Related Art

In a TAB (Tape Automated Bonding) and a flip chip, for example,protrusive connection electrodes (bumps) of gold, copper, solder, ornickel, or layers thereof are formed at predetermined locations(electrodes) on the surface of a semiconductor chip withinterconnections formed thereon, and the semiconductor chip iselectrically connected to package electrodes or TAB electrodes by thosebumps. There are various methods for forming these bumps, includingelectroplating method, vapor deposition method, printing method, andball bump method. As the number of I/O terminals on semiconductor chipsincreases and the pitch thereof decreases, the electroplating method isfinding more use in forming bumps because it can produce smaller bumpsand provide relatively stable performance.

The electroplating method is available in different types in the art.One of those different electroplating methods is a spurting or cupmethod wherein a surface to be plated of a substrate, such as asemiconductor wafer or the like, is horizontally placed so as to facedownwardly, and a plating solution is spurted from below. The othermethod is known as a dipping method wherein a substrate to be plated isvertically erected in a plating tank and a plating solution isintroduced upwardly into the plating tank so as to overflow the platingtank when the substrate is dipped and plated in the plating solutionflowing in the plating tank. The dipping method is advantageous in thatit allows bubbles that would adversely affect the quality of the platedfilm to be easily removed, and the footprint is small. The dippingmethod is therefore considered to be suited for the bump plating inwhich holes to be filling by the plating are relatively large and whichrequires a fairly long plating time.

When using the dipping-type electroplating apparatus to form the bumpthe air bubbles can escape easily. Conventional electroplating apparatusfor carrying out the dipping method have a substrate holder fordetachably holding a substrate, such as a semiconductor wafer or thelike, while sealing its outer circumferential edge and reverse sidesealed, and exposing its surface to be plated. The substrate holder withthe substrate held thereby is dipped in a plating solution to plate thesurface of the substrate.

The substrate holder is required to reliably seal the outercircumferential edge of the substrate for preventing the platingsolution from going there around to the reverse side of the substratewhen the substrate holder holds the substrate. One known substrateholder has a pair of openable and closable supports (holding members)with a presser ring mounted on one of the supports. When the substrateis positioned between the supports, a rotary ring is rotated to pressone of the supports toward the other, pressing a seal ring fixed to oneof the supports against the outer circumferential edge of the substrate,thereby to seal the outer circumferential edge of the substrate and holdthe substrate.

With the above conventional substrate holder, when the presser ring isrotated, one of the supports is pressed toward the other to hold thesubstrate. Upon rotation of the presser ring, the support is deformed,straining the seal ring which finds it considerably difficult to fullyseal the outer circumferential edge of the substrate. Especially, when aplated film is to be embedded in fine recesses defined in the surface ofthe substrate, it is the general practice to use a highly permeativeplating solution which can easily and reliably find its way into thefine recesses. Therefore, the use of such a highly permeative platingsolution makes it more difficult to completely seal the outercircumferential edge of the substrate.

For successively plating a substrate and processing the substrate inconnection with the plating process, it has been customary in the art tohold the substrate with a substrate holder and move the substrate holderwith a transfer device successively through plating and processing tankswherein the substrate held by the substrate holder is dipped in theplating solution and processing liquids.

If a small lot of substrate products are to be manufactured, and thesubstrate is held by the substrate holder and delivered to and processedby the processing tanks, then the transfer device tends to be large insize, and a substrate loading/unloading device is required forhorizontally loading and unloading the substrate. As a result, theoverall plating apparatus is liable to large in size.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide asubstrate holder for detachably holding a substrate while reliablysealing the outer circumferential edge of the substrate, and a platingapparatus which is suitable for the production of a small lot ofsubstrate products and can be reduced in size, and a plating methodwhich is carried out by such a plating apparatus.

According to an aspect of the present invention, there is provided asubstrate holder for holding a substrate, comprising: a seal ring forsealing an outer circumferential edge and a reverse side of thesubstrate, while exposing a surface to be plated of the substrate; abase; a cover having an opening defined therein; and an attractingmechanism for coupling the base and the cover to each other to hold thesubstrate positioned between the base and the cover, with the surface ofthe substrate being exposed through the opening.

The substrate holder can hold the substrate by attracting the cover tothe base with the substrate sandwiched therebetween, without turning ortwisting the cover with respect to the base. Therefore, when thesubstrate holder holds the substrate, the cover and components combinedtherewith are prevented from being unduly deformed and a seal ring isalso prevented from being strained with the deformation of the cover,etc. Consequently, the seal ring can fully seal the substrate.

The attracting mechanism may comprise a vacuum attracting mechanism. Thevacuum attracting mechanism can produce sufficient attractive forces forattracting the cover to the base. When the vacuum attracting mechanismis inactivated, the base and the cover are disconnected from each other,easily and reliably releasing the substrate therebetween.

The base preferably has a provisionally supporting mechanism forprovisionally supporting the substrate on the base. The provisionallysupporting mechanism provisionally supports the substrate on the base,after which the cover is attracted to the base for holding the substratebetween the base and the cover. The provisionally supporting mechanismmay comprise a suction cup of a vacuum-attracting type or the like,which may be positioned centrally on the base.

The substrate holder may further comprise a positioning mechanismdisposed between the base and the cover for positioning the substratedisposed and held between the base and the cover. The positioningmechanism can automatically position the substrate in a predeterminedposition when the substrate is placed and then held between the base andthe cover.

According to another aspect of the present invention, there is alsoprovided a substrate holder for holding a substrate, comprising: a sealring for sealing an outer circumferential edge and a reverse side of thesubstrate, while exposing a surface to be plated of the substrate; and abase and a cover lying vertically and confronting each other; whereinthe base is adapted to attract the substrate in a vertical orientationunder vacuum, and secure the cover to the base in covering relation tothe surface of the substrate with the seal ring pressed against thesubstrate.

In the substrate holder according to the other aspect, the cover has apositioning mechanism for receiving and positioning the substrateattracted under vacuum by the base. The substrate is prevented fromfalling by gravity off the substrate holder by the positioning mechanismwhile the substrate is being positioned and held between the based andthe cover.

According to still another aspect of the present invention, there isprovided a plating apparatus for plating a substrate, comprising: aplating unit having a plating tank for containing a plating solutiontherein, a substrate holder for holding the substrate in a verticalorientation, and a vertically displacing mechanism for verticallydipping the substrate holder and the substrate held thereby in theplating solution in the plating tank; a loading/unloading station forloading and unloading the substrate; and a transfer device fortransferring the substrate between the plating unit and theloading/unloading station.

If the plating apparatus has a plurality of such substrate holdersassociated with respective plating units and plates substrates which arebeing detachably held in the vertical orientation by the respectivesubstrate holders, then plating apparatus is suitable for the productionof a small lot of substrate products, for example, and may be relativelysmall in size.

In the above plating apparatus, the plating unit preferably has a watercleaning tank for cleaning the substrate with water contained therein.Thus, the substrate held in the vertical orientation by the substrateholder can be plated in the plating tank and subsequently cleaned in thewater cleaning tank.

The plating apparatus may further comprises a rinser drier for rinsingand drying the substrate. Thus, the substrate held in the verticalorientation by the substrate holder can be plated and then successivelyrinsed and dried.

According to yet another aspect of the present invention, there isprovided a method of plating a substrate, comprising: transferring thesubstrate to a plating unit with a transfer device; holding thesubstrate with a substrate holder which is supported on a verticallydisplacing mechanism of the plating unit; lowering the substrate withthe vertically displacing mechanism to dip the substrate held by thesubstrate holder in a vertical orientation in a plating solution in theplating unit thereby to plate the substrate; lifting the substrateholder to bring the plated substrate out of the plating solution; andtransferring the plated substrate from the substrate holder to thetransfer device.

According to still yet another aspect of the present invention, there isprovided a method of plating a substrate, comprising: attracting andholding a substrate transferred by a transfer device, with a substrateholder which lies vertically and is lifted; lowering the substrateholder to dip the substrate held by the substrate holder into a platingsolution thereby to plate the substrate; lifting the substrate holder tobring the plated substrate out of the plating solution; and transferringthe plated substrate from the substrate holder to the transfer device.

Each of the above methods may further comprise the step of cleaning theplated substrate in a water cleaning tank after the substrate holder islifted to bring the plated substrate out of the plating solution.

Each of the above methods may further comprise the steps of cleaning theplated substrate received from the substrate holder, drying the cleanedsubstrate, and returning the dried substrate from the transfer device toa loading/unloading station.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate preferredembodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an overall layout of a plating apparatusaccording to an embodiment of the present invention;

FIG. 2 is an enlarged plan view of a plating unit of the platingapparatus shown in FIG. 1;

FIG. 3 is a perspective view of a substrate holder of the platingapparatus shown in FIG. 1;

FIG. 4 is a perspective view of a base of the substrate holder;

FIG. 5 is a perspective view of a cover of the substrate holder;

FIG. 6 is an enlarged fragmentary cross-sectional view of the substrateholder before the substrate holder holds a substrate;

FIG. 7 is an enlarged fragmentary cross-sectional view of the substrateholder after the substrate holder has held a substrate;

FIGS. 8A through 8E are cross-sectional views showing a process ofholding a substrate with the substrate holder;

FIG. 9 is a perspective view of a plating unit, as seen from its frontside, according to another embodiment of the present invention;

FIG. 10 is a perspective view of the plating unit, as seen from its rearside, according to the other embodiment of the present invention; and

FIGS. 11A through 11E are cross-sectional views showing a process offorming a bump (protrusive electrode) on a substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiment of the present invention will be described withreference to FIGS. 1 through 11.

FIG. 1 shows an overall layout of components of a plating apparatusaccording to an embodiment of the present invention. As shown in FIG. 1,the plating apparatus has two cassette tables 10 for placing thereonrespective cassettes which accommodate substrates, such as semiconductorwafers or the like, therein, an aligner 12 for aligning an orientationflat or notch of a substrate with a predetermined direction, and arinser drier 14 for rinsing a plated substrate and rotating the rinsedplated substrate at a high speed to dry the substrate. The cassettetables 10 serve as a loading/unloading station for loading and unloadingsubstrates. The plating apparatus also has a first transfer robot 16movably disposed between the two cassette tables 10, the aligner 12, andthe rinser drier 14, for transferring a substrate to and from the twocassette tables 10, the aligner 12, and the rinser drier 14. The firsttransfer robot 16 has a vacuum-attracting or gravity-positioning handfor transferring a substrate in the horizontal orientation.

In this embodiment, the plating apparatus has a total of four platingunits 20 arranged in a linear array. Each of the plating units 20comprises a plating tank 22 and a water cleaning tank 24 which arepositioned adjacent to each other, and a substrate holder 26 disposedabove the plating tank 22 and the water cleaning tank 24 for detachablyholding a substrate in a vertical orientation. The substrate holder 26is vertically movable by a vertically displacing mechanism 28 andlaterally movable by a laterally displacing mechanism 30. The platingapparatus also has a second transfer robot 32 movably disposed on afront side of the plating units 20 for transferring a substrate to andfrom the aligner 12, the rinser drier 14, and the substrate holder 26 ofeach of the plating units 20. The second transfer robot 32 has e.g. amechanical-chuck hand for holding a substrate, the hand having a turningmechanism 34 for turning the substrate through 90° between a horizontalorientation and a vertical orientation. The second transfer robot 32transfers a substrate to and from the aligner 12 and the rinser drier 14while holding the substrate in the horizontal orientation, and transfersa substrate to and from the substrate holder 26 while holding thesubstrate in the vertical orientation.

The plating tank 22 of each of the plating units 20 is arranged tosupply a plating solution from its bottom into the space in the platingtank 22, and cause the supplied plating solution to overflow an overflowdam on the peripheral wall of the plating tank 22, while a substrate isbeing dipped in the plating solution in the plating tank 22 to plate thesurface of the substrate. As shown in detail in FIG. 2, each of theplating units 20 has an anode 36 disposed in the plating tank 22 in aposition facing the surface of a substrate held by the substrate holder26 in the plating tank 22. The plating unit 20 also has a paddle 40positioned between the substrate held by the substrate holder 26 and theanode 26 and actuatable by a paddle actuator 38 to reciprocally moveparallel to the substrate to uniformize the flow of the platingsolution, and a regulation plate 42 also positioned between thesubstrate and the anode 26 and having a central hole commensurate withthe size of the substrate for lowering the electric potential of thecircumferential edge of the substrate for uniformizing the thickness ofa plated film on the substrate.

A pair of nozzle rods 44 is disposed along upper longitudinal oppositeedges of the water cleaning tank 24. Each of the nozzle rods 44 has aplurality of ejection nozzles 46 spaced at a predetermined pitch forejecting pure water inwardly and downwardly. After a substrate held bythe substrate holder 26 is plated in the plating tank 22, the substrateis removed from the plating tank 22. The substrate holder 26 which isholding the plated substrate is then lowered into the water cleaningtank 24. While the substrate holder 26 is then being lifted, theejection nozzles 46 eject pure water toward the substrate holder 26 towash away the plating solution which has been attached to the surfacesof the substrate and the substrate holder 26. Alternatively, the watercleaning tank 24 may be filled with pure water, the substrate holder 26which is holding the plated substrate may then be placed into the purewater in the water cleaning tank 24, and thereafter the pure water mayquickly be drawn from the water cleaning tank 24 for thereby washingaway, with the pure water, the plating solution which has been attachedto the surfaces of the substrate and the substrate holder 26.

As shown in detail in FIGS. 3 through 7, the substrate holder 26primarily comprises abase 50 and a cover 52 extending vertically andconfronting each other. The base 50 is directly coupled to thevertically displacing mechanism 28, which is mounted on the laterallydisplacing mechanism 30. Therefore, when the vertically displacingmechanism 28 is actuated, the base 50 is vertically moved. When thelaterally displacing mechanism 30 is actuated, the base 50 and thevertically displacing mechanism 28 are laterally moved in unison witheach other.

The base 50 comprises a flat plate 54 and an upper end support 56integrally joined to the upper end of the flat plate 54. The flat plate54 is provided with an annular land 60 which is of a size commensuratewith the size of a substrate to be held by the substrate holder 26. Theannular land 60 has a support surface 58 for abutting against the outercircumferential marginal edge of the substrate. The land 60 also has anouter tapered surface 62 conically tapered off toward the cover 52. Theflat plate 54 also is provided with a suction cup 64 disposedsubstantially centrally in the annular land 60 for provisionallyattracting the substrate, and a plurality of suction cups 66 disposedrespectively at four corners around the annular land 60 for finallyattracting the substrate. These suction cups 64, 66 are of thevacuum-attracting type, for example.

An annular continuous vacuum-attracting groove 68 is defined in the base50 around the annular land 60. As shown in FIGS. 6 and 7, thevacuum-attracting groove 68 communicates with a suction hole 70 definedin and extending through the base 50. The suction hole 70 is connectedto a vacuum pipe extending from a vacuum source, so that thevacuum-attracting groove 68 can be evacuated by the vacuum source.Although not shown, the suction cups 64, 66 are also connected to avacuum source, so that regions surrounded by the peripheral walls of thesuction cups 64, 66 can be evacuated by the vacuum source.

A seal member 72 in the shape of a rectangular frame is fixed to thesurface of the flat plate 54 which faces the cover 52 in surroundingrelation to the suction cups 66, for preventing the plating solutionfrom entering through the gap between the base 50 and the cover 52. Theannular land 60 has a plurality of recesses 74 defined therein andspaced at a predetermined pitch in the circumferential directionthereof. The recesses 74 accommodate therein respective electricconductors (electric contacts) 78 connected respectively to a pluralityof wires 76 which extend in the base 50 and are electrically connectedto a power source.

A linear displacement mechanism 84 is mounted on an upper surface of theupper end support 56 joined to the upper end of the flat plate 54. Thelinear displacement mechanism 84 comprises an actuator such as acylinder or the like, a slider 80 coupled to the actuator, and a guide82 for guiding the slider 80. When the actuator is operated, the slider80 is linearly displaced along the guide 82 in directions transverse tothe flat plate 54. The cover 52, on the other hand, comprises a support90 fixed to an upper surface of the slider 80 of the linear displacementmechanism 84, and a flat cover plate 92 suspended from the support 90downwardly. When the slider 80 is linearly moved by the actuator of thelinear displacement mechanism 84, the cover 52 is linearly displacedtoward and away from the base 50.

The flat cover plate 92 has a circular opening 94 defined centrallytherein for exposing therethrough the surface to be plated of thesubstrate which is held by the substrate holder 26. The circular opening94 has a peripheral wall including a tapered surface 96 closer to thebase 50 and tapered off away from the base 50 for complementarilyfitting over the tapered surface 62 of the land 60 of the base 50. Thetapered surfaces 62, 96 jointly make up a positioning mechanism forpositioning the base 50 and the cover 52 relatively to each other.Specifically, when the cover 52 is displaced into intimate contact withthe base 50, the land 60 of the base 50 is fitted into the opening 94 inthe cover 52. At this time, the tapered surface 96 of the opening 94 isguided by the tapered surface 62 of the land 60, positioning the cover52 with respect to the base 50. As shown in FIGS. 8A through 8E, thecover 52 has a substrate retainer 100, which comprises two pinsaccording to this embodiment, disposed on the surface of the cover 52which faces the base 50 at a position near the opening 94. The substrateretainer 100 positions the substrate thereon for preventing thesubstrate from falling by gravity when the substrate is held between thebase 50 and the cover 52. The positioning of the substrate is performedwith substrate retainer 100.

The peripheral wall of the circular opening 94 also includes a flatsurface next to the tapered surface 96 remotely from the base 50. Theflat surface supports thereon a seal ring 102 for being pressed againstthe outer circumferential edge of the substrate to seal the same in awater-tight fashion when the substrate is held between the base 50 andthe cover 52. The tapered surface 96 has a plurality of recesses 104defined therein and spaced at a predetermined pitch in thecircumferential direction of the tapered surface 96. The recesses 104accommodate therein respective electrodes 108 for supplying electricenergy to the substrate when the substrate is held between the base 50and the cover 52. As shown in FIGS. 6 and 7, the electrodes 108 areelectrically connected to the respective electric conductors 78 (seeFIG. 4) on the base 50 through respective tongues 106 on the base 50.

An O-ring 110 is fixedly mounted on the base 50 radially inwardly of thevacuum-attracting groove 68 defined in the base 50 and radially spaced apredetermined distance from the seal member 72. A vacuum-attracting area112 is provided between the O-ring 110 and the seal member 72. When thebase 50 and the cover 52 are put together, the tip ends of the O-ring110 and the seal member 72 are held against the surface of the cover 52,and the vacuum-attracting groove 68 and the vacuum-attracting area 112which communicates with the vacuum-attracting groove 68 are evacuated bythe vacuum source connected to the vacuum-attracting groove 68, therebycompressing the tip ends of the O-ring 110 and the seal member 72 toprovide a water-tight seal between the base 50 and the cover 52.

The flat cover plate 92 has a plurality of vacuum-attracting cavities114 defined therein at respective positions aligned with the suctioncups 66 for finally attracting the substrate on the base 50. Thevacuum-attracting cavities 114 are complementary in size and profile tothe suction cups 66. When the base 50 and the cover 52 are put together,the suction cups 66 have respective ends positioned in thevacuum-attracting cavities 114. A vacuum developed in the suction cups66 then attracts the cavities 114 and hence the cover 52 to the base 50.

A process of holding a substrate W with the substrate holder 26 will bedescribed below with reference to FIGS. 8A through 8E.

As shown in FIG. 8A, the base 50 and the cover 52 are spaced apredetermined distance from each other. Then, the substrate W heldvertically by the second transfer robot 32 is positioned between thebase 50 and the cover 52. After the substrate W is brought into abutmentagainst the surface of the base 50 by the second transfer robot 32, thesuction cup 64 is evacuated to provisionally attract the substrate W tothe surface of the base 50, as shown in FIG. 8B.

In this state, as shown in FIG. 8C, the cover 52 is moved toward thebase 50 by the linear displacement mechanism 84 until the substrateretainer 100 of the cover 52 is positioned beneath the substrate Wprovisionally secured in position by the suction cup 64 of the base 50.Then, as shown in FIG. 8D, the suction cup 64 is inactivated to releasethe substrate W, which then falls by gravity onto the substrate retainer100. The substrate W is now positioned on its edge.

As shown in FIG. 8E, the cover 52 is further moved toward the base 50.At this time, the tapered surface 96 of the opening 94 in the cover 52is guided onto the tapered surface 62 of the land 60 of the base 50,thus positioning the cover 52 with respect to the base 50. Therefore,the substrate W which has been released from the suction cup 64 isplaced in its free state between the base 50 and the cover 52. When theends of the suction cups 66 enter the vacuum-attracting cavities 114defined in the flat cover plate 92, for example, the linear displacementmechanism 84 is inactivated to stop the cover 52 against movement towardthe base 50.

Then, the suction cups 66 are evacuated to attract the cover 52 to thebase 50, reliably holding the substrate W between the base 50 and thecover 52. The vacuum-attracting groove 68 and the vacuum-attracting area112 which is provided between the 0-ring 110 and the seal member 72 andcommunicates with the vacuum-attracting groove 68 are evacuated to sealthe flat cover plate 92 around the opening 94 in a water-tight fashionwith the seal ring 102.

At this time, as shown in FIG. 7, the seal member 72 of the base 50 ispressed against the surface of the flat cover plate 92 to seal betweenthe base 50 and the surface of the flat cover plate 92, thereby toprevent a plating solution from entering through the gap between thebase 50 and the cover 52. Furthermore, the tip end of the seal ring 102disposed within the opening 94 defined in the flat cover plate 92 ispressed against the outer circumferential edge of the substrate W heldbetween the base 50 and the cover 52, thus sealing the outercircumferential edge of the substrate W with the seal ring 102.Simultaneously, the tongues 106, which are connected to the electricconductors 78 connected to the wires 76, are pressed against therespective electrodes 108 on the cover 52, and the outer circumferentialedge of the substrate W held between the base 50 and the cover 52 ispressed against the electrodes 108. Thus, the substrate W is suppliedwith electric energy from the power source.

Thus, the tongues 106 and the electrodes 108 for supplying electricenergy to the substrate W are exposed within a region that is sealedbetween the seal member 72 and the seal ring 102. Therefore, the tongues106 and the electrodes 108 are reliably prevented from contacting theplating solution.

The surface to be plated of the substrate W is exposed out through theopening 94 of the cover 52. The outer circumferential edge of thesubstrate W is sealed by the seal ring 102 against entry of the platingsolution. The gap between the base 50 and the cover 52 is sealed by adual-seal structure made up of the seal member 72 and the O-ring 110.

After the substrate W is plated, the substrate W held by the substrateholder 26 will be released therefrom by a process which is essentiallythe reversal of the above process, and transferred to the secondtransfer robot 32.

A plating process carried out by the above plating apparatus will bedescribed, as a process of forming a bump (protrusive electrode) on asubstrate, below with reference to FIGS. 11A through 11E. As shown inFIG. 11A, a seed layer 500 as an electric supply layer is formed on thesurface of a substrate W. After the entire surface of the seed layer 500is coated with a resist 502 having a height H of e.g. 20-120 μm, anopening 502 a having a diameter D of e.g. 20-200 μm is formed at aprescribed position in the resist 502. The substrate W is then placed ina cassette in which the surface to be plated of the substrate W facesupwardly. Thereafter, the cassette is placed on one of the cassettetables 10.

The first transfer robot 16 takes out one substrate W from the cassetteon the cassette table 10, and puts the substrate W on the aligner 12,which aligns an orientation flat or notch of the substrate W with apredetermined direction. The substrate W thus oriented by the aligner 12is taken from the aligner 12 by the second transfer robot 32, and turned90° from the horizontal orientation to the vertical orientation by theturning mechanism 34. The second transfer robot 32 then transfers theturned substrate W to the substrate holder 26 of a selected one of theplating units 20.

In the present embodiment, the substrate W is transferred to thesubstrate holder 26 above the water cleaning tank 24. Specifically, thesubstrate holder 26 has been lifted by the vertically displacingmechanism 28 and laterally displaced to the water cleaning tank 24 sideby the laterally displacing mechanism 30, and receives the substrate Wfrom the second transfer robot 32 and holds the substrate W in thevertical orientation. At this time, the surface to be plated of thesubstrate W held by the substrate holder 26 is exposed through theopening 94 in the cover 52, and the substrate W has its outercircumferential edge sealed by the seal ring 102, with the seed layer500 contacting the electrodes 108 for being supplied with an electriccurrent therefrom.

The substrate holder 26 which is holding the substrate W in the verticalorientation is moved to the plating tank 22 side by the laterallydisplacing mechanism 30. The plating tank 22 has been supplied with aplating solution from its bottom such that the plating solutionoverflows the overflow dam on the peripheral wall of the plating tank22. Then, the substrate holder 26 which is holding the substrate W islowered into the plating tank 22 by the vertically displacing mechanism28, dipping the substrate W in the plating solution. A plating voltageis applied between the anode 36 and the substrate W, and at the sametime the paddle actuator 38 moves the paddle 40 reciprocally parallel tothe surface of the substrate W, thus plating the surface of thesubstrate W. At this time, the seed layer 500 (see FIG. 11A) of thesubstrate W is supplied with an electric current through the wires 76,the electric conductors 78, the tongues 106, and the electrodes 108.

After the substrate W is plated, the application of the plating voltageis stopped, and the paddle actuator 38 is inactivated to stop moving thepaddle 40. The substrate holder 26 which is holding the plated substrateW is lifted out of the plating tank 22 by the vertically displacingmechanism 28.

Thereafter, the substrate holder 26 which is holding the substrate W inthe vertical orientation is moved to the water cleaning tank 24 side bythe laterally displacing mechanism 30. Then, the substrate holder 26which is holding the substrate W is lowered into the water cleaning tank24 by the vertically displacing mechanism 28. Now, while the substrateholder 26 is being lifted, the ejection nozzles 46 eject pure watertoward the substrate holder 26 to wash away the plating solution whichhas been attached to the surfaces of the substrate W and the substrateholder 26. Alternatively, as described above, the water cleaning tank 24maybe filled with pure water, the substrate holder 26 which is holdingthe substrate W may then be placed into the pure water in the watercleaning tank 24, and thereafter the pure water may quickly be drawnfrom the water cleaning tank 24 for thereby washing away, with the purewater, the plating solution which has been attached to the surfaces ofthe substrate W and the substrate holder 26. As a further alternative, acombination of the above-described two cleaning schemes may be used toclean the substrate W and the substrate holder 26.

The second transfer robot 32 receives the cleaned substrate W in thevertical orientation from the substrate holder 26 above the watercleaning tank 24. Then, the turning mechanism 34 of the second transferrobot 32 turns the substrate W through 90° from the vertical orientationto the horizontal orientation. The second transfer robot 32 transfersthe turned substrate W to the rinser drier 14 and places the substrate Win the rinser drier 14.

The rinser drier 14 rinses the substrate W and spins the substrate W ata high speed to spin dry the substrate W. The dried substrate W is thentransferred from the rinser drier 14 back in to the cassette on thecassette table 10 by the first transfer robot 16 to complete theprocess. As shown in FIG. 11B, the substrate W plated and processed, asdescribed above, has a plated film 504 grown in the opening 502 a formedin the resist 502.

Thereafter, the dried substrate W is dipped in a solvent, such asacetone or the like, that is maintained at a temperature of 50-60° C.,for example, whereupon the resist 502 is removed from the substrate W,as shown in FIG. 11C. Then, as shown in FIG. 11D, the unnecessary seedlayer 500 exposed after the plating process is removed from thesubstrate W. Thereafter, heat is applied to reflow the plated film 504on the substrate W, thus forming a bump 506 which is made round undersurface tension as shown in FIG. 11E. Then, the substrate W is annealedat a temperature of, for example, 100° C. or higher, thereby removingresidual stress in the bump 506.

When the substrate holder 26 is not in use, i.e., when the substrateholder 26 is not holding a substrate, the substrate holder 26 is dippedin pure water filled in the water cleaning tank 24. When the substrateholder 26 is dipped in pure water, any plating solution attached to thesubstrate holder 26 is solidified on the surface of the substrate holder26 and prevented from producing particles which would otherwiseadversely affect the plating process on substrates W.

FIGS. 9 and 10 show a plating unit 20 according to another embodiment ofthe present invention. The plating unit 20 comprises a plating tank 22and a water cleaning tank 24 which are positioned adjacent to eachother, and a substrate holder 26 disposed above the plating tank 22 andthe water cleaning tank 24 for detachably holding a substrate in avertical orientation. The substrate holder 26 is vertically movable by avertically displacing mechanism 28 and movable back and forth by aback-and-forth displacing mechanism 120. When the back-and-forthdisplacing mechanism 120 is actuated, the substrate holder 26 is movedback and forth between the plating tank 22 and the water cleaning tank24. Other structural details of the plating unit 20 shown in FIGS. 9 and10 are identical to those of the plating unit 20 shown in FIGS. 1through 8.

As described hereinabove, the substrate holder 26 according to thepresent invention can hold the substrate W by attracting the cover 52 tothe base 50 with the substrate W sandwiched therebetween, withoutturning or twisting the cover 52 with respect to the base 50. Therefore,when the substrate holder 26 holds the substrate W, the cover 52 andcomponents combined therewith are prevented from being unduly deformedand the seal ring 102 is also prevented from being strained.Consequently, the seal ring 102 can fully seal the outer circumferentialmarginal edge of the substrate W. The plating apparatus has a pluralityof such substrate holders 26 associated with respective plating units 20and plates substrates W which are being detachably held in the verticalorientation by the respective substrate holders 26. The platingapparatus thus arranged is suitable for the production of a small lot ofsubstrate products, and may be relatively small in size.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

1. A substrate holder for holding a substrate, comprising: a seal ringfor sealing an outer circumferential edge and a reverse side of thesubstrate, while exposing a surface of the substrate; a base; a coverhaving an opening defined therein; and an attracting mechanism forcoupling said base and said cover to each other to hold said substratepositioned between said base and said cover, with said surface of thesubstrate being exposed through said opening.
 2. A substrate holderaccording to claim 1, wherein said attracting mechanism comprises avacuum attracting mechanism.
 3. A substrate holder according to claim 1,wherein said base has a provisionally supporting mechanism forprovisionally supporting said substrate on said base.
 4. A substrateholder according to claim 1, further comprising: a positioning mechanismprovided between said base and said cover for positioning said substratedisposed and held between said base and said cover.
 5. A substrateholder for holding a substrate, comprising: a seal ring for sealing anouter circumferential edge and a reverse side of the substrate, whileexposing a surface to be plated of the substrate; and a base and a coverlying vertically and confronting each other; wherein said base isadapted to attract the substrate in a vertical orientation under vacuum,and secure said cover to said base in covering relation to the surfaceof the substrate with said seal ring pressed against said substrate. 6.A substrate holder according to claim 5, wherein said cover has apositioning mechanism for receiving and positioning said substrateattracted under vacuum by said base.